Antenna with integrated condensation control system

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 13/707,307 entitled “Antenna with Integrated Condensation Control System,” filed Dec. 6, 2012, which application claims priority to U.S. Provisional Application No. 61/567,586, entitled “Mobile Antenna,” which was filed on Dec. 6, 2011, the contents of each of which are hereby incorporated by reference for any purpose in their entirety.

FIELD OF INVENTION

The present disclosure relates generally to condensation control systems in airborne radio frequency (RF) antenna devices, and specifically to passive condensation control systems including a desiccant airflow channel integral with the RF device and functionally located between an air volume internal to the RF device and ambient air.

BACKGROUND

Feed horn type RF antenna devices typically have internal air volumes associated with the feed horn. For example, an air cavity typically exists within the interior of a feed horn. This interior space can be typically connected to a waveguide cavity. The feed horn can further be covered with an aperture close-out and otherwise sealed to keep moisture out of this interior space.

If the pressure inside this interior air volume increases sufficiently, however, it is possible that the aperture close-out or other seals could rupture or be degraded to the point that moisture can enter the RF device. As discussed herein, moisture within the internal air volume of feed horn type RF antenna devices can significantly degrade the performance of the RF device. To illustrate this point, <figref idref="DRAWINGS">FIG. 9</figref> illustrates the severe impact of one drop of water placed in each of 8 ports of an 8:1 RF combiner. As can be seen, there can be relatively little difference between the performance of a dry waveguide and a waveguide with water at the flange interface. However, the performance can be severely degraded if water is located near the power dividers where RF current densities can be the highest. This can be particularly true in Ku and Ka band frequency RF devices. In smaller, single feed horn RF antenna devices, it may be possible to minimize the total internal air volume such that sealing the device may work. However, sealing an antenna device can be less of an option in larger systems and systems that operate in changing environments.

In particular, an array-type airborne RF antenna would likely burst the seals or aperture close-out if built as a sealed internal air volume. Sealed array-type airborne RF antennas can generate pressure differentials between the internal air volume and ambient air, due to the interior air volume and altitude or temperature changes. Therefore, typically an array-type airborne RF antenna may be vented to the ambient air. Such venting facilitates pressure equalization between the internal air volume and ambient air. Unfortunately, when built as a vented air volume, moisture can enter the interior air volume. Therefore, many complex solutions have been used to prevent condensation and/or reduce moisture in the air in the internal air volume of RF antennas of this type. These complex solutions are expensive, unreliable, heavy and/or large, in-efficient, and in general undesirable.

A new device, system and method for moisture and condensation control is now described.

SUMMARY

In an example embodiment, an airborne radio frequency (RF) antenna device can comprise: a radiating portion; a waveguide portion connected to the radiating portion; a desiccant airflow channel; and an internal air volume located within the RF antenna device and associated with the desiccant airflow channel. The desiccant airflow channel can be integral with the RF antenna device. The internal air volume can be vented to the environment outside of the RF antenna device through the desiccant airflow channel.

An airborne mobile radio frequency (RF) antenna device can comprise: an aperture grid plate; and an aperture horn plate attached to the aperture grid plate. The aperture horn plate can further comprise a passive integrated condensation control system comprising a desiccant airflow channel. The integrated condensation control system can be integral with the aperture horn plate. The antenna device can further comprise: azimuth combiners attached to the aperture horn plate, wherein the azimuth combiners can comprise first interconnected waveguides; and elevation combiners attached to the azimuth combiners. The elevation combiners can comprise second interconnected waveguides that can be configured to interconnect the first interconnected waveguides of a plurality of said azimuth combiners. The antenna device can further comprise: an internal air volume that can comprise the space inside a plurality of horns of the aperture horn plate, as well as the space within the first and second interconnected waveguides that can be connected to the plurality of horns, and the space within the aperture grid plate that extends from the plurality of horns.

A method of passive condensation control in an airborne RF antenna device having an internal air volume vented to atmosphere can comprise: flying the airborne RF antenna device to a high altitude; passing air between the internal air volume and the atmosphere via a passive integrated desiccant air flow channel that can be integrated into the RF antenna; and flying the airborne RF antenna device to a low altitude and protecting the internal air volume by absorbing moisture from air passing passively into the internal air volume from the external environment. The passive integrated desiccant air flow channel can comprise a cold regenerative type desiccant.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Additional aspects of the present invention will become evident upon reviewing the non-limiting embodiments described in the specification and the claims taken in conjunction with the accompanying figures, wherein like numerals designate like elements, and:

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of an example RF antenna aperture and positioner;

<figref idref="DRAWINGS">FIG. 2</figref> is an exploded perspective view of an example RF antenna aperture, illustrating various example components of the example RF antenna aperture;

<figref idref="DRAWINGS">FIG. 3</figref> is a perspective view of an example RF antenna aperture horn plate with an example integrated desiccant channel component, and showing example vent holes therefrom;

<figref idref="DRAWINGS">FIG. 4</figref> is an exploded perspective view of an example RF antenna aperture horn plate with an example integrated desiccant channel component, and showing an example interior structure thereof;

<figref idref="DRAWINGS">FIG. 5</figref> is another exploded perspective view of an example RF antenna with an example integrated desiccant channel component;

<figref idref="DRAWINGS">FIG. 6</figref> is an exploded perspective view of a filter screen portion of an example integrated desiccant channel component;

<figref idref="DRAWINGS">FIG. 7</figref> is an end view of a portion of an example integrated desiccant chamber;

<figref idref="DRAWINGS">FIG. 8</figref> is an exploded perspective view of a filter screen portion of an example integrated desiccant channel component;

<figref idref="DRAWINGS">FIG. 9</figref> is a graph illustrating the impact of a droplet of moisture located in each port of an RF combiner;

<figref idref="DRAWINGS">FIG. 10</figref> is a flow chart for an example method disclosed herein; and

<figref idref="DRAWINGS">FIGS. 11-12</figref> are perspective views of a filter screen portion of an example integrated desiccant channel component.

DETAILED DESCRIPTION

Reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention.

Many complex solutions have been used to prevent condensation and/or reduce moisture in the air in the internal air volume of RF antennas. For example, some approaches to condensation control include the addition of moisture/condensation control hardware onto existing hardware. One solution involves supplying a dry nitrogen purge to the interior air volume. Another solution employs condensation control tubes that cool the tubes to control where the moisture condenses. Additional control hardware can result in a large increase in hardware mass, increase in hardware footprint volume, increased part count and increased cost of manufacturing. Other solutions are disadvantageous because the location of venting ports or the venting port geometries make design difficult or cause degradation in the performance of the RF antenna. Some solutions connecting external desiccant systems require discreet parts, tubing, and fittings. These provide greater opportunity for breakdowns. Other solutions require power to run pumps, valves, or heaters. In addition to the added complexity, and the power consumption, these solutions can lead to inadvertent problems. For example, if the RF antenna is taken out of service for a few days, not only is it likely that the antenna will be powered off, but the condensation control system may become un-powered, too. Thus, the RF antenna may be unprotected from moisture condensation during that time period. New solutions are presented herein.

In accordance with various aspects, an airborne mobile RF antenna device can comprise an internal air volume, located within the RF antenna device, and a desiccant airflow channel. The internal air volume can be vented to the environment outside of the RF antenna through the desiccant airflow channel. Thus, the internal air volume can be non-hermetically sealed. In an example embodiment, the desiccant airflow channel can be integral with the RF antenna device. In various embodiments, the desiccant airflow channel can be integrated into an aperture horn plate. Thus, an airborne mobile RF antenna device can be configured with a passive integrated condensation control system.

With reference now to <figref idref="DRAWINGS">FIG. 1</figref>, in an example embodiment, an RF antenna <b>100</b> can comprise an antenna aperture <b>110</b> and a positioner <b>120</b>. In an example embodiment, antenna aperture <b>110</b> can comprise an array of antenna horn elements connected via a combiner network. Positioner <b>120</b> can be a single or multi-axis mechanical antenna pointing system. Positioner <b>120</b> can be configured to point antenna aperture <b>110</b> at a satellite. In particular, positioner <b>120</b> can be configured to point antenna aperture <b>110</b> at a satellite as the RF antenna and/or satellite move relative to one another. For example, RF antenna system <b>100</b> can be located on an airplane. Antenna aperture <b>110</b> can be configured to send and receive RF signals between the satellite and RF antenna system <b>100</b>. In this manner, RF antenna system <b>100</b> can be configured to facilitate providing communication, internet connectivity, and the like to passengers on a commercial airline. Moreover, in one example embodiment, RF antenna system <b>100</b> can provide RF signal communication to a satellite from an airborne or otherwise mobile platform, be it commercial, personal, or military.

Antenna aperture <b>110</b> can comprise an aperture horn plate, aperture grid plate, aperture close out, azimuth combiners and elevation combiners. With reference now to FIG. <b>2</b>, antenna aperture <b>210</b> can comprise an aperture close out <b>230</b>, aperture grid plate <b>240</b>, aperture horn plate <b>250</b>, and azimuth and elevation combiners <b>260</b>.

Aperture horn plate <b>250</b> can comprise an array of feed horns in a plate like structure. Aperture horn plate <b>250</b> can be attached proximate to aperture grid plate <b>240</b> on a first “aperture side” of aperture horn plate <b>250</b>. Aperture grid plate <b>240</b> can comprise a grid or array of box like walls. Aperture grid plate <b>240</b> can be configured to separate signals received at the aperture of antenna <b>210</b> and channel those signals to each individual feed horn of aperture horn plate <b>250</b>.

Azimuth and elevation combiners <b>260</b> can be attached proximate to aperture horn plate <b>250</b> and on the side opposite of aperture grid plate <b>240</b>. Azimuth and elevation combiners <b>260</b> can comprise a network of waveguides. Stated another way, azimuth and elevation combiners <b>260</b> can comprise more than one interconnected waveguides. In one example embodiment, azimuth and elevation combiners <b>260</b> can connect a waveguide to each feed horn of aperture horn plate <b>250</b>. The waveguides of azimuth and elevation combiners <b>260</b> can be configured to combine the signals from each connected waveguide into a single signal input/output. Thus, azimuth and elevation combiners <b>260</b> can be configured to combine the RF signal from a plurality of feed horns of the aperture horn plate into a single RF signal.

Aperture close-out <b>230</b> can be connected to aperture grid plate <b>240</b>. Aperture close-out <b>230</b> can be connected to aperture grid plate <b>240</b> on the side of aperture grid plate <b>240</b> that is opposite aperture horn plate <b>250</b>. In one example embodiment, aperture close-out <b>230</b> can be a RF window. For example, Nelco 9200. This material can possess low dielectric and loss tangent properties that can minimize RF performance degradation as RF signals propagate through the window. Other suitable materials with similar RF properties such as polytetrafluoroethylene (PTFE) could also be used. Moreover, aperture close out <b>230</b> can be any material suitably configured to seal off the aperture grid plate and protect the interior air cavity of the aperture grid plate and horn plate from moisture or debris, while still allowing the RF signals to pass through.

Thus, antenna aperture <b>210</b> can comprise an internal air volume. The internal air volume, in one example, can be defined as the cavity that is bounded on one end by aperture close out <b>230</b> and formed within (1) the interstitial spaces formed by aperture grid plate <b>240</b>, (2) within the interior cavities of the various feed horns, and/or (3) within the various waveguides of the waveguide combiners connected to the feed horns of aperture horn plate <b>250</b>. Stated another way, the internal air volume can comprise the space inside at least one horn, and generally a plurality of horns, of the aperture horn plate. The internal air volume can comprise the space extending from the plurality of horns through the grid plate. The internal air volume can comprise the space within the plurality of interconnected waveguides that are connected to the plurality of feed horns. The internal air volume can comprise at least one of these spaces.

Moreover, the internal air volume can comprise all the air volume internal to RF antenna aperture <b>210</b>. In other embodiments, the internal air volume can be defined as a sub-portion of all the air volume internal to antenna aperture <b>210</b>. Furthermore, the internal air volume can further include air volumes extending in additional waveguide(s) and cavities connected to azimuth and elevation combiners <b>260</b>.

In an example embodiment, RF antenna <b>100</b> comprises a passive integrated condensation control system. The passive condensation control system can be formed integral with any suitable component of RF antenna <b>100</b>. For example, the passive condensation control system can be formed integral with aperture <b>210</b>. Moreover, in one example embodiment, the passive condensation control system can be formed integral with aperture horn plate <b>250</b>. In other example embodiments, not shown, the passive condensation control system can be integral with aperture grid plate <b>240</b> or azimuth combiner <b>260</b>. Regardless of where on antenna <b>100</b> the passive condensation control system is integrated, it is noted that the integration of the passive condensation control system can be a significant benefit. Integration of the passive condensation control system can facilitate creating a compact, space efficient, light weight antenna. Integration can facilitate use of no external hardware, no discrete parts, no tubing, and/or no fittings. In stating that this can be implemented without fittings, it is intended that, in an example embodiment, the system can have no tubing interface fittings or similar plumbing type pipe interface fittings. Thus, the integrated passive condensation control system can be configured to provide a light weight and small antenna. This can be very useful for airborne satellite antennas where reduction in antenna mass can reduce aircraft service costs. In addition, a small antenna's swept volume under the aerodynamic fairing radome can facilitate a reduction in radome size and aerodynamic drag which again can reduce aircraft service costs.

With reference now to <figref idref="DRAWINGS">FIG. 3</figref>, aperture horn plate <b>350</b> can comprise a passive integrated condensation control system <b>370</b>. As shown in <figref idref="DRAWINGS">FIG. 3</figref>, aperture horn plate can comprise multiple feed horns <b>351</b>. Feed horns <b>351</b> can be arranged in any suitable array, grid, or pattern. For example, feed horns <b>351</b> can be arranged in rows of feed horns. In one example embodiment illustrated in <figref idref="DRAWINGS">FIG. 3</figref>, feed horns <b>351</b> can be laid out in 8 rows of feed horns in aperture horn plate <b>350</b>. Passive integrated condensation control system <b>370</b> can be located along one side of aperture horn plate <b>350</b>. In one example embodiment, passive integrated condensation control system <b>370</b> can be located along the long edge of aperture horn plate <b>350</b>. Moreover, passive integrated condensation control system <b>370</b> can be located along more than one edge of aperture horn plate <b>350</b>. In this example embodiment, the desiccant channel may wrap around at least a portion of the horn plate increasing the length of the desiccant channel. Thus, the passive integrated condensation control system <b>370</b> can be integral with the aperture horn plate. Moreover, passive integrated condensation control system <b>370</b> can be located in any suitable location integral with aperture horn plate <b>350</b>. Passive integrated condensation control system <b>370</b> can comprise a desiccant airflow channel. Thus, in one example embodiment, aperture horn plate <b>350</b> can comprise a desiccant airflow channel that can be integral with the aperture horn plate.

Passive integrated condensation control system <b>370</b> can be connected to the internal air volume via vent holes <b>371</b>. In one embodiment, aperture horn plate <b>350</b> can comprise holes providing an air passage way between passive integrated condensation control system <b>370</b> and the internal air volume. It should be recognized that by providing vent holes <b>371</b> to at least one feed horn <b>351</b>, because the various feed horns can be interconnected via the waveguide combiners, passive integrated condensation control system <b>370</b> can be connected to all of the interconnected feed horns of aperture horn plate <b>350</b>. In <figref idref="DRAWINGS">FIG. 3</figref>, it can be seen that vent holes <b>371</b> can be provided to two feed horns <b>351</b>. In an example embodiment, vent hole(s) <b>371</b> can be connected to the internal air volume at a low current area of the system. For example, compared to various portions of the waveguide combiner structure, the aperture horn plate can be a low current area of structure defining the internal air volume. Moreover, in an example embodiment, where the structure defining the internal air volume can comprise multiple repetitive (similar to each other) parts (e.g., the azimuth combiners), the vent hole(s) can be connected to the internal air volume at a non-repetitive part (e.g., the aperture horn plate). In an example embodiment, the vent hole(s) can be connected to the internal air volume at a portion of the structure that can be common each port of the array.

In an example embodiment vent holes <b>371</b> can be round, oval, rectangular, or any suitable shape. In an example embodiment, vent holes <b>371</b> can be similar in size to Bethe hole couplers, wherein an individual hole can couple a very small amount of RF energy (typically less than 30 dB). In an example embodiment, a connected feed horn can be connected by a single vent hole <b>371</b>. In other example embodiments, a feed horn can be connected by two vent holes <b>371</b>. Moreover, vent holes <b>371</b> can be any size, shape, number and dimension sufficient to provide enough air flow between passive integrated condensation control system <b>370</b> and the internal air volume to control condensation within the antenna system consistent with the principles described herein.

With reference now to <figref idref="DRAWINGS">FIG. 4</figref>, an aperture horn plate <b>450</b> can comprise feed horns <b>451</b> and a passive integrated condensation control system <b>470</b>. Passive integrated condensation control system <b>470</b> can comprise a desiccant air flow channel <b>473</b> that can be integral with aperture horn plate <b>450</b>. Desiccant air flow channel <b>473</b> can be configured to vent the internal air volume to the environment outside of the RF antenna device through desiccant airflow channel <b>473</b>. Although described herein as the “environment outside of the RF antenna,” other equivalent terms can be used such as “external environment” or “ambient air.”

Passive integrated condensation control system <b>470</b> can comprise at least one vent hole opening to at least one feed horn <b>451</b>. In an example embodiment, a first vent hole <b>471</b> can open to a feed horn <b>451</b> and a second vent hole <b>471</b> can open to a second feed horn <b>451</b>. Vent holes <b>471</b> can be configured to provide an air passage way between the internal air volume and desiccant air flow channel <b>473</b>. Moreover, desiccant air flow channel <b>473</b> can open to the external environment via an exterior port <b>474</b>. Thus, air can flow from the internal air volume through vent hole <b>471</b>, through desiccant air flow channel <b>473</b>, and through exterior port <b>474</b>. Exterior port <b>474</b>, similar to vent hole <b>471</b>, can be of any suitable shape, size, number, and dimension to facilitate sufficient air flow through desiccant air flow channel <b>473</b>. Stated another way, desiccant air flow channel <b>473</b> can comprise: a first port connecting an open space in desiccant airflow channel <b>473</b> to the internal air volume; and a second port connecting the open space in desiccant airflow channel <b>473</b> to the external environment. In various example embodiments, the first port can be a first air ingress/egress port and the second port can be a second air ingress/egress port. Stated yet another way, desiccant air flow channel <b>473</b> can comprise a channel structure having a first end opening to the internal air volume and a second end opening to the environment. Stated another way, desiccant air flow channel <b>473</b> comprises an open space facilitating airflow between the internal air volume and the external environment.

In one embodiment, desiccant air flow channel <b>473</b> can comprise a serpentine airflow channel. The serpentine airflow channel effectively increases the length of the airflow channel <b>473</b> between the vent port <b>471</b> and external port <b>474</b>. The serpentine air flow channel can be configured to increase dwell time of the air passing through the desiccant material in the channel. Thus, the length and course (e.g., serpentine) of the airflow channel can be designed to achieve a desired air/desiccant interaction. Typically, the longer the channel, the better, so in one embodiment, the integrated condensation control system <b>470</b> can be integrated on the long edge of the aperture horn plate <b>450</b>. As mentioned before, in another example embodiment, the channel may be made longer by wrapping it around more than one side of aperture horn plate <b>450</b>. In another example the desiccant channel can be made longer by wrapping the channel back and adjacent to itself one or more times on a common side.

Desiccant air flow channel <b>473</b> can be a chamber or airflow channel that is filled with a desiccant material. The integrated condensation control system therefore can be a packed bed desiccant air flow channel. The desiccant material located in desiccant air flow channel <b>473</b> can, in one example embodiment, be aluminum dioxide. Moreover, the desiccant material can be: molecular sieve, silica gel, montmorillonite clay, calcium sulfate, calcium chloride. Furthermore, any suitable desiccant material can be used that dries the air within the internal air volume under the circumstances contemplated herein. For example, that dries the air within the internal air volume while cycling between (1) relatively higher altitude, drier air and (2) relatively lower altitude, moister air. The desiccant material can be selected to optimize air drying for the intended environmental conditions.

In an example embodiment, high altitude may be from 10,000 feet to 40,000 feet. Stated another way, cruising altitude for an airplane bearing the RF antenna may be approximately 35,000 feet. In various example embodiments, cruising altitude can be at a high altitude. At these relatively higher altitudes, the atmospheric pressure may be approximately 20 to 30 kPa. In an example embodiment, low altitude may be from 300 feet below sea level to 5,500 feet above sea level. At these relatively lower altitudes, the atmospheric pressure may be approximately 100 kPa.

In one example embodiment, integrated condensation control system <b>470</b> can comprise two desiccant air flow channels. For example, integrated condensation control system <b>470</b> can comprise a primary desiccant air flow channel <b>473</b> and a redundant desiccant air flow channel <b>483</b>. In this embodiment, primary desiccant air flow channel <b>473</b> can comprise a first primary port <b>471</b> and a second primary port <b>474</b>, and redundant desiccant air flow channel <b>483</b> can comprise a first redundant port <b>481</b> and a second redundant port <b>484</b>. The first primary and redundant ports <b>471</b>/<b>481</b> can connect the respective desiccant air flow channels <b>473</b>/<b>483</b> to the internal air volume. The second primary and redundant ports <b>474</b>/<b>484</b> can connect the respective desiccant air flow channels <b>473</b>/<b>483</b> to the exterior environment. In the illustrated example embodiment of <figref idref="DRAWINGS">FIG. 4</figref>, the second primary and redundant ports can be located in approximately the center of the long side of aperture horn plate <b>450</b> and thus can be located proximate to each other. In this case, in one example embodiment, a filter screen <b>485</b> can be configured to cover both the second primary port <b>474</b> and second redundant port <b>484</b>.

In an example embodiment, integrated condensation control system <b>470</b> can comprise a first filter screen <b>472</b> at first port <b>471</b> and a second filter screen at the second port <b>474</b>. In a primary/redundant embodiment, the first primary port(s) <b>471</b> and or first redundant port(s) <b>481</b> can be covered with filter screens <b>472</b>/<b>482</b>, respectively. The first filter screens <b>472</b>/<b>482</b> can be configured to be located between desiccant airflow channel <b>473</b>/<b>483</b> and the internal air volume. The second filter screen <b>485</b> can be configured to be located between desiccant airflow channel and the exterior environment.

In one embodiment, the filter screens can be made of a perforated metal sieve. In other example embodiments, the filter screens can be a microporous expanded PTFE (ePTFE) membrane or similar porous metallic, plastic or glass material. Moreover, the filter screens, internal filter screens <b>472</b>/<b>482</b> or external filter screens (e.g., <b>485</b>), can be any filter screen configured to (1) retain desiccant particles within the desiccant airflow channel, (2) while allowing air to pass through desiccant airflow channel(s) <b>473</b>/<b>483</b> between the internal air volume and the external environment, and (3) that will allow sufficient pressure equalization (reducing differential pressure gradients between ambient environment and internal hardware air cavity).

For example, a microporous ePTFE membrane prevents pressure build up by constantly equalizing the difference in pressure between the inside of the enclosure and its immediate environment. This can reduce the pressure on the seals. The filter can be configured to allow air and other gases to pass through the membrane freely but stop liquids from entering the enclosure. It is noted that even small air pressure differentials can have an detrimental impact on large surface area components such as the aperture close-out <b>230</b>. Thus, filter screens can be selected to have low airflow resistance so as to not induce a large pressure differential.

In an example embodiment, integrated condensation control system <b>470</b> comprises a cover plate <b>490</b>. Cover plate <b>490</b> can be located proximate to the desiccant air flow channel and between the desiccant air flow channel and the exterior environment. Cover plate <b>490</b> can be made of aluminum or any suitable non-porous material. Cover plate <b>490</b> can be generally flat and sized to cover the channel and vent ports. Furthermore, cover plate <b>490</b> can be any size, shape or material suitable for retaining the desiccant material within desiccant air flow channel <b>473</b>/<b>483</b>. Cover plate <b>490</b> can be attached using any suitable fastener, to aperture horn plate <b>450</b>. In one example embodiment, cover plate <b>490</b> can be removable for replacing the desiccant. In another example embodiment, cover plate <b>490</b> comprises some or all of the desiccant channel when attached to aperture horn plate <b>450</b>.

With momentary reference to <figref idref="DRAWINGS">FIGS. 5-8, 11 and 12</figref>, an example antenna is illustrated in <figref idref="DRAWINGS">FIG. 5</figref> showing the location of the passive integrated condensation control system <b>470</b> in the overall assembly, with components already discussed identified by similar reference numbers.

In accordance with various aspects, an example method of protecting a vented internal air volume of an RF antenna using integrated passive condensation control, including an integrated desiccant air flow channel filled with desiccant, comprises absorbing moisture from relatively moist air flowing into the internal air volume while the RF antenna descends through low altitude regions, absorbing moisture that might otherwise reach the internal air volume while the RF antenna remains at ground level, and regenerating the desiccant while the RF antenna descends through high altitude regions. The method further comprising regenerating the desiccant while cruising at a relatively high altitude.

In accordance with various aspects, and with reference to <figref idref="DRAWINGS">FIG. 10</figref>, a description of use of the integrated passive condensation control system is described in the context of an airborne RF antenna. A method <b>1000</b> for providing passive condensation control, in an airborne RF antenna device having an internal air volume vented to atmosphere, can comprise the operation of regenerating a desiccant in the integrated passive condensation control system by flying the airborne RF antenna device to a high altitude (operation <b>1010</b>). The high altitude can mean an altitude higher than 10,000 feet above sea level, or to an altitude where the air is drier than the humidity level within the desiccant. Thus, in one embodiment, this operation can comprise movement of the device to a dry air environment having relatively lower atmospheric pressure than the starting point. In accordance with an example embodiment, the integrated passive condensation control system can be configured to maintain the relative humidity in the internal air volume below the dew point.

During the ascent and descent phases of the flight, atmospheric pressure decreases and increases, and the air in the internal air volume can expand and contract. In other words, the decrease and increase in altitude can cause a pressure differential between the inner air volume and the exterior environment that causes a net flow of air in and out of the internal air volume, by way of the desiccant air flow channel. The air at high altitude regions can be relatively dry. As this dry air flows through the desiccant, the absorbed moisture in the desiccant can be released to the dry air, facilitating the regeneration of the desiccant.

The method can further comprise regenerating the desiccant while cruising at relatively higher altitude (operation <b>1020</b>). In this phase, the desiccant may continue to exchange moisture away from the desiccant and into the relatively dry air of the exterior environment.

The method can further comprise protecting the internal air volume from moisture by absorbing moisture during a descent in altitude (operation <b>1030</b>). During a descent, the ambient air pressure can increase causing air inside the internal air volume to contract and generate an air flow from the external environment into the internal air volume. The desiccant can absorb moisture in the infiltrating air, protecting the internal air volume. Moreover, while stationed at a relatively lower altitude with relatively warmer and moister air, the desiccant can continue absorbing moisture to protect the internal air volume (operation <b>1040</b>).

It is noted that to implement this method, one merely has to move/cycle (operation <b>1050</b>) the RF antenna from a moist low altitude environment to a dry high altitude environment. Although the relative humidity of the internal air volume can fluctuate during each cycle, even if initially very humid, the internal air volume can reach a “steady state” where the relative humidity can be low. This can be done with no external hardware, no discrete components, no power to operate fans or pumps or heaters, no fittings, and no tubing.

This can be useful because the antenna can be protected even if it is turned off/powered off. In contrast, a pump, valve, or heater implemented solution may not protect the internal air volume from moisture if powered off/out of service. The antenna can even be protected for a period of time if it is left on a shelf or parked on the ground (until the desiccant saturates). The passive regenerative air dryer solution can be low maintenance and has no moving parts. In an example embodiment, a “passive” device can be a device that has no electrical external power source (e.g., battery or generator). This can be done while also minimizing pressure differentials between the ambient environment and the air cavity within the hardware structure.

The waveguide combiner/dividers that can define part of the internal air volume can be comprised of H-plane T-junction type waveguide combiners/dividers. In one example embodiment, the H-plane T-junction waveguide combiner comprises an offset asymmetric septum and in another example embodiment, the H-plane T-junction waveguide combiner comprises an E-plane septum as discussed in more detail in a co-filed patent application, U.S. application Ser. No. 13/707,049, entitled “In-Phase H-Plane Waveguide T-Junction With E-Plane Septum,” filed Dec. 6, 2012, and incorporated herein by reference.

RF antenna systems, related power distribution networks, and methods of making the same can be further described in U.S. patent application Ser. No. 13/707,160, entitled “Dual-Circular Polarized Antenna System,” and filed Dec. 6, 2012 on the same date as this application, which is incorporated herein by reference in its entirety.

In describing the present invention, the following terminology will be used: The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an item includes reference to one or more items. The term “ones” refers to one, two, or more, and generally applies to the selection of some or all of a quantity. The term “plurality” refers to two or more of an item. The term “about” means quantities, dimensions, sizes, formulations, parameters, shapes and other characteristics need not be exact, but may be approximated and/or larger or smaller, as desired, reflecting acceptable tolerances, conversion factors, rounding off, measurement error and the like and other factors known to those of skill in the art. The term “substantially” means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. Numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also interpreted to include all of the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 1 to 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3 and 4 and sub-ranges such as 1-3, 2-4 and 3-5, etc. This same principle applies to ranges reciting only one numerical value (e.g., “greater than about 1”) and should apply regardless of the breadth of the range or the characteristics being described. A plurality of items may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. Furthermore, where the terms “and” and “or” are used in conjunction with a list of items, they are to be interpreted broadly, in that any one or more of the listed items may be used alone or in combination with other listed items. The term “alternatively” refers to selection of one of two or more alternatives, and is not intended to limit the selection to only those listed alternatives or to only one of the listed alternatives at a time, unless the context clearly indicates otherwise.

It should be appreciated that the particular implementations shown and described herein are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the present invention in any way. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical device.

As one skilled in the art will appreciate, the mechanism of the present invention may be suitably configured in any of several ways. It should be understood that the mechanism described herein with reference to the figures is but one exemplary embodiment of the invention and is not intended to limit the scope of the invention as described above.

It should be understood, however, that the detailed description and specific examples, while indicating exemplary embodiments of the present invention, are given for purposes of illustration only and not of limitation. Many changes and modifications within the scope of the instant invention may be made without departing from the spirit thereof, and the invention includes all such modifications. The corresponding structures, materials, acts, and equivalents of all elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed. The scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given above. For example, the operations recited in any method claims may be executed in any order and are not limited to the order presented in the claims. Moreover, no element is essential to the practice of the invention unless specifically described herein as “critical” or “essential.”